Generally, a circuit of a high-frequency device, like a tuner of a cable television, is constructed of a plurality of circuit blocks, each of which is mutually shielded by a shield plate so as to be prevented from mutual electromagnetic interference. The required electric connection is obtained by a feedthrough capacitor connected between a circuit outside the shield case and the above-described circuit block or between two circuit blocks.
As an example of a high-frequency device of this kind, a structure of a tuner of a cable television is shown in FIGS. 7 and 8.
As shown in FIG. 7, tuner 1 has frame-shaped shield case 4 formed of two metal plates 2 and 3 having the same width. One of the metal plates 2 forming case 4 has sides bent at a right angle from both ends thereof, which sides are connected by the other metal plate 3. The inside of the case 4 is divided by shield plates 5 into a plurality of small sections 6. Within respective sections 6 are secured circuit blocks 7 as shown in FIG. 8.
To facilitate production efficiency of tuner 1, adjacent circuit blocks 7 are integrally constructed on a printed substrate 9 having the parts mutually connected by means of connecting portions 8, with required electronic components 11 (see FIG. 9) mounted thereon. Upon fixing an appropriate circuit block 7 to the inside of each small section 6 of case 4, respective portions 8 fit in notches 12 formed in shield plates 5, and shield plates 5 are fitted into slits 13 between adjacent blocks 7. Within shield case 4 the printed substrate 9 is positioned at a position defined by the position of notches 12 formed in plates 5 and projections 14 on case 4.
In fixing hole portions 16 for feedthrough capacitors 15 and formed in case 4 or plates 5 are fixed feedthrough capacitors 15 and the external conductors formed on the surface thereof are soldered to shield case 4 of shield plates 5, whereby the required electric connections are obtained between a circuit (not shown) outside of case 4 and the above-described circuit blocks 7, or between two circuit blocks 7. In FIGS. 7 and 8 an example is shown wherein feedthrough capacitor 15 is fixed to metal plate 3 forming the shield case 4.
At the top and bottom of shield case 4 covers are provided (not shown), having slits which engage with torsion tabs 18 formed on case 4, and the covers are secured by twisting said tabs.
A tuner 1 of a cable television having such a construction has conventionally had a structure for fixing a feedthrough capacitor 15 as explained below.
A fixing hole 16 for a feedthrough capacitor 15 is positioned in case 4 or a plate 5 in such a manner that the feedthrough capacitor 15 is above the surface on the opposite side of substrate 9 from wiring pattern-containing surface 9a of the printed substrate 9 as shown in FIG. 9, and a connecting portion 8 of the circuit block 7 is brought into contact with the bottom of notch 12 in a shield plate 5 and printed substrate 9 abuts against a projection 14 of the shield case 4. The external conductor of a capacitor 15 fixed to the portion of the case 4 around hole 16 and is soldered to case 4 or plate 5 and the feedthrough terminal 19 thereof which is bent midway of its length at a right angle and is inserted through hole 9b of substrate 9 from the side opposite to the wiring pattern-containing surface 9a (see FIG. 8) of substrate 9 together with the terminals of other electronic components 11, and then the structure is immersed into molten solder 21 to solder the terminals to the wiring pattern (not shown) of circuit block 7 (printed substrate 9), as shown in FIG. 9.
With such a conventional structure for fixing a feedthrough capacitor 15 as described above, the fixing hole portion 16 therefor is formed in the shield case 4 or shield plate 5 spaced from the side of substrate 9 opposite to pattern-containing surface 9a of substrate 9. For this reason, the fixing structure has posed a problem in that, prior to simultaneous processes of immersing into molten solder 21 and soldering the terminals to the pattern of circuit block 7 (printed substrate 9) the feedthrough terminal 19 of capacitor 15 must be inserted through a hole (not shown) in substrate 9 together with terminals of electronic components 11, which process necessitates much time and labor in fixing the feedthrough capacitor 15. In this process, it is first necessary to fit capacitor 15 in the hole portion 16 and solder the external conductor of the conventional structure for fixing the feedthrough capacitor 15, solder which solders the external conductor of capacitor 15 to the shield case 4 or shield plate 5 may be melted by the heat generated at the time of immersing the case 4 and substrate 9 into molten solder 21, thus causing the feedthrough capacitor 15 to be tilted.
Hence, the problem to be solved by the present invention is to provide a structure for both fixing a feedthrough capacitor in a high-frequency device wherein electronic components are to be soldered to the wiring pattern on a printed substrate at the same time, and permitting the soldering of the feedthrough capacitor to the shield case or shield plate, and to provide a method of manufacturing such a high-frequency device.